A shock absorber, a cylinder device, and the like include a tubular member such as a cylinder, and a shaft member such as a piston rod. The shock absorber generates a damping force using a working fluid such as a working oil. The cylinder device drives a target object by the working fluid. The working fluid is housed in the tubular member. The shaft member is axially movably inserted into the tubular member. The shock absorber and the cylinder device are extendable and compressible due to relative movements between the tubular member and the shaft member. A seal member is provided between the tubular member and the shaft member. The seal member prevents the working fluid from leaking from the tubular member.
A shock absorber for a front fork which suspends a front wheel in a straddled vehicle such as a motorcycle includes a shock absorber main body made up of an outer tube (tubular member) and an inner tube (shaft member). The outer tube is joined to one of a vehicle body side and a vehicle wheel side. The inner tube is joined to the other of the vehicle body side and the vehicle wheel side, and is axially movably inserted into the outer tube. The shock absorber main body houses a working fluid therein, and includes a seal member which seals an opening of a tubular gap on an outer air side, the tubular gap being formed in a portion where the outer tube and the inner tube overlap.
In the front fork, mud, sand, and the like (hereinafter referred to as “foreign substances”) easily adhere to an outer circumferential surface of the inner tube while the vehicle is running. JP 2013-002622A and JP 2012-180883A disclose a seal member for an oil seal and a seal member for a dust seal which are arranged in series. The seal member for an oil seal includes an oil lip which prevents a working fluid inside a shock absorber main body from flowing out, whereas the seal member for a dust seal includes a dust lip which scrapes off foreign substances adhering to an outer circumferential surface of an inner tube. In this way, the seal member for a dust seal scrapes off the foreign substances. This makes it possible to not only prevent the foreign substances from entering the inside of the shock absorber main body, but also prevent the working fluid from leaking externally due to damage to a sliding surface of the oil lip caused by the foreign substances adhering to the inner tube.
Also, in the foregoing front fork, the inner tube may bend or incline with respect to the outer tube due to application of an external force. In view of this, by increasing the length of a dust lip, the dust lip more highly conforms to the inner tube. The high conformity suppresses the dust lip from being separated from the inner tube and thus being placed in an open state.